(1) Field of the Invention
The present invention relates to improvements in a cutting installation for cutting out blanks from a sheet material band, such as "prepregs" carrying a cover layer on one or both surfaces, which comprises a cutting table comprising a conveyor band forming a working surface and operable to move in a conveying direction, and a source of low pressure applicable thereto, a cutting head movable over the working surface of the conveyor band, the cutting head comprising a cutting tool preferably vertically adjustable to a desired cutting depth, a sheet material band supply station arranged upstream of the conveyor band in the conveying direction, and a sheet material band receiving station arranged downstream of the conveyor band in the conveying direction.
(2) Description of the Prior Art
In the art of manufacturing fiber-reinforced synthetic resins, "prepregs" are understood to be pre-impregnated fibrous structures which are impregnated with a predetermined proportion of a synthetic resin mass which is heat-curable without any additives. These structures may be covered by a film on one or both surfaces thereof and formed into a sheet material band, which may be reeled into a sheet material band supply roll, and this sheet material band is then fed to a suitable cutting installation to cut out blanks of a desired configuration. To minimize waste, the individual blanks should be as close together as possible to form a cutting pattern. The sheet material band is held on the cutting table by the low pressure applied to the working surface and the cutting tool may be an ultrasonically vibrated cutting knife for automatically cutting the blanks out of the sheet material band, the conveyor band of the cutting table being guided above suction boxes under the cutting table. The conveyor band is intermittently moved in the conveying direction to provide the required sections of working surface and, at the same time, serves to convey the sheet material band from the supply to the receiving station, the sheet material band being reeled off onto the conveyor band at the supply station and being deposited from the conveyor band on the receiving station. In these known cutting installations, the sheet material band is cut into respective lengths corresponding to the length of the working surface sections at the supply station and each cut length of the sheet material band is then worked on the cutting table separately, which means that the cutting operation must be adapted to a limited length of cutting pattern. Since the individual blanks are closely spaced in this pattern, this leaves limited freedom of patterning and a correspondingly large amount of waste. Furthermore, it is impossible to separate the blanks from the waste on the cutting table immediately after the blanks have been cut out, except by time-consuming manual labor, and the blanks are delivered to the receiving station together with the waste.
British patent No. 2,040,778 deals with the manufacture of die cut vinyl lettering, wherein a continuous strip of a vinyl film/release coated card laminate is fed onto an intermittently moving carrier band and is thereby moved to a cutting station for cutting letters out of the strip. The resultant blanks are then blown by compressed air into a vacuum box where they are collected on a mesh and the die-cut letter pieces are then deposited in a downstream receiving station by reversing the carrier band. In this way, the waste or scrap is automatically separated but this procedure can be used only for individual, sequentially arranged blanks of a very simple configuration and cannot be used for complex cutting patterns or in cutting installations of the first-described type.